fix(ai-sessions): restore a refused prompt's context and drop the stale idle entry

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/lib/components/copilot/chat/AIChatManager.svelte.ts

@@ -1801,10 +1801,16 @@ export class AIChatManager {
 			// fall back on — the raw-app inline prompt would lose what the user
 			// typed outright. Not `restoreToInput`, whose no-composer fallback is
 			// the very queue being refused.
-			const restored = this.aiChatInput?.prependText(text, images, files) === true
-			if (restored) this.#restoreDomContext(context, true)
+			const composer = this.aiChatInput
+			if (composer) {
+				// `prependText` answers "did this land on top of a draft already being
+				// written", not "did it land at all" — it always restores. Its return
+				// is what tells #restoreDomContext whether to keep the existing chips
+				// as well as the restored ones.
+				this.#restoreDomContext(context, composer.prependText(text, images, files))
+			}
 			sendUserToast(
-				restored
+				composer
 					? 'This session is running in another tab. Your prompt is waiting in the composer.'
 					: 'This session is running in another tab. Try again when it finishes.',
 				true

frontend/src/lib/components/sessions/sessionRunOwner.svelte.ts

@@ -98,7 +98,14 @@ export function noteDriverAlive(sessionId: string, planMode: boolean): void {
  *  the truthful position rather than merely the convenient one. */
 export function noteRemoteTurnEnded(sessionId: string): void {
 	if (runPosition(sessionId).state !== 'watching') return
-	positions.set(sessionId, canCompleteCatchUp() ? { state: 'catchingUp' } : { state: 'idle' })
+	// Deleted rather than set to idle: a missing entry already reads as idle, and
+	// the tab this branch exists for has no runtime, so nothing in it would ever
+	// call clearRunPosition to take the entry back out again.
+	if (!canCompleteCatchUp()) {
+		positions.delete(sessionId)
+		return
+	}
+	positions.set(sessionId, { state: 'catchingUp' })
 }
 
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